Human beings sense the depth of an object through a subtle difference of the same object observed by left and right eyes, thus recognizing a stereoscopic image of the object. This difference is called parallax. The stereoscopic display technology is producing parallax of left and right eyes of an observer by artificial means and sending two parallactic images to the left and right eyes of the observer, so that the brain generates a real stereoscopic feeling after acquiring the two parallactic images observed by the left and right eyes.
To meet preferences of different users (some users expect to experience stereoscopic display effects, while some users expect to experience flat panel display effects), flat panel display/stereoscopic display switching mechanisms have been provided in some display devices and thus allow the display devices to show different display effects according to the selections of users.
In the prior art, a display device capable of realizing a switchover of flat panel display/stereoscopic display includes a display panel and a liquid crystal grating disposed on a light emergent side of the display panel. During the flat panel display, the liquid crystal grating is a light transmittable surface; and during the stereoscopic display, the liquid crystal grating is a plurality of light transmittable stripes and a plurality of shading stripes which are arranged at interval. The liquid crystal grating cooperates with the display panel to allow the left eye of a user to see a left-eye image only and the right eye to see a right-eye image only and there is a parallax between the left-eye image and the right-eye image, so that the stereoscopic display is realized. Although the switchover of flat panel display/stereoscopic display may be realized by the liquid crystal grating, yet the display device including the liquid crystal grating has complicated structure, relatively high cost, low utilization of a light source and high energy consumption.
In the prior art, there is also a display device for realizing the switchover of flat panel display/stereoscopic display by using a lens assembly. This lens assembly includes concave lenses and convex lenses fitting in with the concave lenses. Both the concave lenses and the convex lenses are made of a birefringent material. The refractive index of one of the concave lenses is equal to that of a corresponding one of the convex lenses; moreover, for a polarized light in a certain particular polarization direction, the concave lenses show an ordinary refractive index, while the convex lenses show an extraordinary refractive index. To realize a switchover between flat panel display and stereoscopic display, the display device also needs to be configured with a switchable polarizer. The switchable polarizer may be switched between a first polarization mode in which a first polarized component of light can pass through the polarizer and a second polarization mode in which a second polarized component of the light can pass through the polarizer. This display device including the lens assembly has relatively complicated structure and high cost.
Therefore, how to realize a switchover between flat panel display and stereoscopic display with a simple structure has become an urgent technical problem to be solved in the art.